virgl: fix stride + layer_stride inconsistency

With blob resources, stride doesn't necesarily have to
equal width * bpp.  The use case for this a minigbm blob
resource with blob mem BLOB_MEM_HOST3D_GUEST imported into
guest Mesa.  In addition, for BLOB_MEM_HOST we can repurpose
the transfer ioctls to also flush caches if need be, so this
seems a good time to fix this issue.

Reviewed-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/4821>
3 files changed